Heretofore, in a vertical CVD apparatus and the like, a boat having holder plates has been used as a substrate holder which holds plural wafers (for example, Patent Document 1). As shown in FIG. 15 and FIG. 16, the boat has four support columns 32 provided vertically. The support columns are arranged in a range of an approximate semi-circumference so as to make it possible to load and unload the wafers. Ring-like quartz-made holder plates 33 are welded in a horizontal attitude at multi-stages to groove portions (not shown) provided on the support columns 32. On an upper surface of each holder plate 33, plural support claw portions 34 are provided as substrate mounting portions which mount the wafer thereon.
When wafer processing, for example, film forming is performed on the wafers by using the boat as described above, the quartz-made holder plates 33 uniform a flow of processing gas on surfaces of the wafers, thus making it possible to restrict only a film thickness of ends of the wafers from being thickened. Moreover, the wafers are held on the support claw portions 34 provided on the holder plates 33 more inside than the four support columns 32 arranged on the approximate semi-circumference. Accordingly, a distance between the columns 32 and the wafers is lengthened. Therefore, an effect of the support columns 32 is reduced, thus making it possible to enhance uniformity of the film thickness.
Patent Document 1: Japanese Patent Laid-Open Publication No. H11-40509 (FIG. 5, FIG. 6, FIG. 7, FIG. 10)